CT excitation of [Ir(azulene)(1,5-cyclooctadiene)]+. Spectroscopy and photochemistry

The complex [Ir(azulene)(1,5-cyclocta-diene)]+ shows long-wavelength absorptions which are assigned to spin-allowed (λmax = 536 nm) and spin-forbidden (675 nm) transitions. They are of mixed MLCT (Ir → azulene) and ILCT (azulene) character. At 77 K the solid complex displays an emission (λmax = 816 nm) which originates from the MLCT/ILCT triplet. At r.t. in solution the complex undergoes a photosubstitution of the azulene ligand. It is suggested that in the CT state the azulene ligand looses its coordinating ability.